1. Field of the Invention
The present invention relates to a device for detecting an edge of a transparent sheet of a laminated transparent and translucent sheet assembly as an assembly of two transparent glass sheets between which a translucent interlayer is sandwiched. The present invention further relates to laminated safety glass for an automobile windshield, etc. and to an apparatus for cutting off, in production of laminated safety glass, a protruding end portion of an interlayer sandwiched between two glass sheets.
2. Description of the Prior Art
Generally, an automobile windshield is formed from laminated safety glass which consists of two glass sheets and an interlayer of polyvinyl butyral or the like sandwiched between the glass sheets and bonded to same.
In production of laminated safety glass, the interlayer is first sized a little larger than the glass sheets and then cut to size after sandwiched between the glass sheets by cutting off its end portion protruding from the glass sheets. After that, the glass sheet and interlayer assembly is processed by tacking rolls for initial adhesion and then by an autoclave for permanent fastening.
In order to cut off the protruding end portion of the interlayer, it has been practiced to first locate the glass sheet and interlayer assembly in place, i.e., in a predetermined base position by means of locating tools adapted for abutment upon the corresponding edges of one of the glass sheets which are nearly rectangular and then cut off the protruding end portion of the interlayer by means of a cutter adapted to move along a predetermined path which is fixedly set on the basis of the base position of the assembly.
With the prior art cutting apparatus, cutting of the protruding end portion of the interlayer is carried out without detecting the edges of the glass sheets and thereby knowing whether the glass sheet and interlayer assembly is located in place.
A problem of the prior apparatus is that the protruding end portion of the interlayer may possibly be turned up and sandwiched between some locating tool or tools and the corresponding edge or edges of the glass sheet, causing the assembly to be largely moved out of place, i.e., out of the base position and therefore variations in cutting off of the interlayer and, in some cases, causing damage of the cutter and the edges of the glass sheets.